This invention relates to the transport of materials and, more particularly, to the automatic transport of sheet material.
It is often necessary to transport sheet material. For example, corrugated or cardboard sheets, which are often received in stack form and are loaded into a hopper of the unit that feeds the sheets to a press to be imprinted with a desired legend.
Although the stacks can be transported manually from a receiving dock and then manually loaded into the hopper, it is desirable to completely automate the handling of the stacks. For that purpose, a number of systems have been proposed, such as those disclosed in U.S. Pat. No. 3,422,969 which issued to J. A. Miller, et al. on Jan. 21, 1969, and U.S. Pat. No. 3,643,939 which issued to H. A. Nussbaum et al. on Feb. 22, 1972. These systems involve the transport of a stack to a position where the stack is upset to permit shingling feed of the sheets to an output location.
The foregoing and other prior art systems have a number of disadvantages. In each case, for example, if there is a mechanical or other failure which requires temporary shutdown of the system for repair, the interposition of the system between the receiving or input station and the output location, interferes with the continued use of the output equipment.
Moreover, in the case of U.S. Pat. No. 3,422,969, upset of the stack for transport to the output location takes place on an incline, as shown in FIG. 2 of the patent, so that the weight of the sheets against one another can interfere with the desired output feed. In addition, as shown in FIG. 3 of the patent, the upset is achieved by the tilting of slats which form a backrest. The slats have to be lowered sufficiently to reduce the weight of the upper sheets of the stack against the lower sheets that are being shingled, but, as a result, there is an inadequate gravitational effect for the proper feed of the upper sheets along the slats.
The system of U.S. Pat. No. 3,422,969 further employs an output conveyor which has a greater angle of inclination than the inclined conveyor that feeds sheets to it. This change in angle of inclination produces a further impediment to the proper feed of sheets to the output location because the impact of the oncoming sheets can produce so much pressure against the sheets on the incline that jamming can result. The system also employs electric motors to drive the conveyors and operate the slats that upset the stack. To produce the necessary drive torque, the motors require significant speed reduction, which adds to the mechanical disadvantages of the system.
The mechanical disadvantages of U.S. Pat. No. 3,422,969 are present to an even greater degree in U.S. Pat. No. 3,643,939, where it is necessary to employ a transfer conveyor that requires rotation with a full load through an angle greater than 90 degrees. In this system electric motors are used to operate the conveyors, but the transfer conveyor is elevated and lowered hydraulically.
Furthermore, the foregoing and other prior art systems have no way of controlling the throughput of the system to assure a continuous, adequate supply of material at the output of the system.
Accordingly, it is an object of the invention to facilitate the automatic transport of sheets of material from an input position to an output position. A related object is to facilitate the upset of a stack of materials and the shingled feed of the upset stack to the output position.
Another object of the invention is to provide a transport system which will not prevent the through-flow of materials when the system is temporarily shutdown, for example, for repair.
Still another object of the invention is to eliminate the need for slats to act as a backrest during the upset of materials that are to be automatically transported to an output position.
A further object is to facilitate the shingling of upset materials, both during upset and during subsequent transport of the sheets to the output position.
A yet further object is to operate the system with a common motive source for upsetting the stack and moving the conveyors.
A still further object of the invention is to control the throughput of the system to insure a continuous and adequate supply of material at the system output.